在使用互斥锁的时候，我发现

let x = *l2.lock().unwrap();

这一行会同时释放锁，所以try_lock可以正常获取到

fn main() {
    let l1 = Arc::new(Mutex::new(21));
    let l2 = Arc::clone(&l1);
    let t1 = thread::spawn(move ||{
        let x = *l2.lock().unwrap();
        thread::sleep(Duration::from_secs(10));
    });
    thread::sleep(Duration::from_secs(2));
    let _ = l1.try_lock().expect("get lock error");
}

而下面这段锁的作用域会持续到子线程结束，导致主线程的try_lock()获取失败

fn main() {
    let l1 = Arc::new(Mutex::new(21));
    let l2 = Arc::clone(&l1);
    let t1 = thread::spawn(move ||{
        let x = l2.lock().unwrap();
        let num = *x;
        println!("{}", num);
        thread::sleep(Duration::from_secs(10));
    });

    thread::sleep(Duration::from_secs(2));
    let _ = l1.try_lock().expect("get lock error");
}

我想知道*解引用时发生了什么?